Disclosed are methods to remove organic and/or inorganic compounds (e.g., contaminants) from water containing organic and/or inorganic compounds, involving contacting the water with a hemoglobin/Fe3O4 composite where the compounds in the water adsorb onto the hemoglobin/Fe3O4 composite, and removing (e.g., using a magnet since the composite is magnetic) the hemoglobin/Fe3O4 composite from the water.
Dyes are used in a variety of industries including paper, paint, textile, and leather manufacture (Hashem, A., et al., Energy Edu. Sci. Technol., 19: 69-86 (2007)). Dye-contaminated wastewater from textile plants is recognized as one of the most polluting industrial wastewater, especially considering the amount of water used and the content of the discharge effluent (Chequer, F. M. D., et al., Textile dyes: dyeing process and environmental impact, 2013: INTECH Open Access Publisher). Wastewater from these industries show a lot of variations in wastewater characteristics such as biochemical oxygen demand (BOD), color intensity, and chemical oxygen demand (COD). It has been reported that a significant amount of synthetic dyes (about 12%) used in the manufacturing and processing operations are lost, and roughly 20% of these lost dyes find their way into industrial wastewaters (Weber, E. J., et al., Water Res., 27: 63-67 (1993); Clarke, E. A., et al., Organic dyes and pigments, 181-215 (1980)). Even low concentration of dyes in effluents from the dye industries significantly decrease the clarity of water and are highly undesirable (Nigam, P., et al., Bioresour. Technol., 72: 219-226 (2000)). The dyes in effluents are of primary concern because of their harmful effects in the environment and also to humans (Robinson, T., et al., Bioresour. Technol., 77: 247-255 (2001)). Unfortunately, because of their high stability to temperature, detergents, and light, just to name a few, they elude most conventional treatment technologies.
Dye contaminated wastewater can be treated with adsorbents. Recently, various authors have used different adsorbents to remove various dyes from aqueous solutions with varying degrees of success (Robati, D., et al., Chem. Eng. J., 284: 687-697 (2016); S. Dhananasekaran, S., et al., J. Adv. Res., 7: 113-124 (2016); Gautam, R. K., et al., J. Environ. Chem. Eng., 3: 79-88 (2015)). Most of the commonly used adsorbents are very high-priced, are hard to recover and recycle, and above all suffer from high activation and reactivation costs. However, we considered hemoglobin (Hb), a globular protein, which is a substance that is inexpensive and may have good properties that will cause organic and/or inorganic compounds (e.g., dyes) to adsorb to Hb. Hb has both positive and negative charges on its surface and therefore may serve as a good candidate for it attachment or attraction to other compounds. Annually, approximately 2 million tons of animal blood are produced in the US as a by-product from slaughterhouses (Del Hoyo, P., et al., Meat Sci., 76: 402-410 (2007)). Most of this blood is used in relatively low value animal feed applications or the blood may end up polluting the water that is being discharged into a wastewater stream. However, hemoglobin (Hb) can easily be isolated from blood and we found it can be used as a starting material for the preparation of hemoglobin/iron oxide composite, thereby minimizing agricultural waste. This will also serve as a good way of converting waste into useful products.
Magnetic particles (particles which show response to magnetic field gradients) exist in different sizes and shapes. Among the various magnetic particles, iron oxide magnetic particles have received considerable attention, and currently are the only magnetic particle type approved for clinical use in the United States (Neuberger, T., et al., J. Magn. Magn. Mater., 293: 483-496 (2005)). Magnetic particles have found a lot of applications including biosensing (Diez, P., et al., J. Colloid Interface Sci., 386: 181-188 (2012)), magnetic storage media (Reiss, G., and A. Hutten, Nat. Mater., 4: 725-726 (2005)), and biomedical applications such as drug delivery and multi-imaging (Lee, J.-H., et al., Mol. Cells, 35: 274-284 (2013)). A nanohybrid, consisting of magnetite attached to exfoliated silica platelets, has been developed for attracting bacteria in microbiological media (Liu, T.-Y., et al., ACS Appl. Mater. Interfaces, 8: 411-418 (2016)). The magnetite attached to silicate platelets greatly helps in the capturing and destruction of the bacterial cells, and subsequently removing them using an external magnet. These broad applications of magnetic nanoparticles are mainly as a result of their non-toxicity, biodegradability, and ease of synthesis (Wiogo, H. T., et al., Langmuir, 28: 4346-4356 (2012)). Magnetized compounds utilized in magnetic separation offers a unique advantage when it comes to the recovery of the spent separating agent because of the ease of separation. Despite advances in magnetic nanoparticles, not all sectors have come to appreciate the importance and other potential applications of magnetic substances. We found that the syntheses of hemoglobin/iron oxide composite is highly practical because hemoglobin can easily be isolated from blood (a meat processing by-product), and incorporating the magnetic properties of magnetite will enhance its recovery from aqueous wastewater. This is therefore an innovative way of converting waste in to a value-added product of commercial importance.
Herein we show how co-precipitation of Hb and iron oxide can produce a novel composite material (Hb/Fe3O4) that surprisingly exhibits good adsorption properties for organic and/or inorganic compounds, and has highly beneficial properties for recovery and re-use of the composite. We also provide details regarding the morphology, thermal stability, and adsorption properties of the novel hemoglobin/iron oxide composite (Hb/Fe3O4) and it application for the removal of organic and/or inorganic compounds from aqueous solutions.